Patent GB-452031-A (GB)
Title: Improvements in or relating to communication systems
IPC: H04L1/14
Filed: 1935-02-15
Abstract: 452,031. Type printing telegraphy. INTERNATIONAL BUSINESS MACHINES CORPORATION, 270, Broadway, New York, U.S.A.-(Assignees of Lemmon, W. S.) Feb. 15, 1935, No. 4921. Convention date, Feb. 23, 1934. [Class 40 (iii)] In a system for distant control of typeprinting telegraphs, card-punching devices or the like in which each character is denoted by a single impulse, signals are repeated back from the receiver to the transmitter in order to verify correctness of reception. In the system shown, each character is denoted by the phase in the rotation of a distributer at which a condenser individual to that character is charged. At the transmitter, depression of a key 1 individual to any letter discharges the corresponding condenser 18. When next the distributer arm 7 reaches the corresponding segment 6, the condenser is recharged and the resulting potential-drop in the resistance 19 causes an impulse to be transmitted. At the receiver the incoming impulse passes via the distributer arm 281 to that one of the keys 1<1> which corresponds to the particular segment 271 through which the impulse was received. The key prints a character with the type-bar 4<1> and also short-circuits the corresponding condenser 38<1>, the subsequent charging of which causes a tell-tale signal to be sent back at the right moment through distributer 5<1> and line or radio link L to operate the tell-tale receiver PA at the transmitting station by way of receiving distributer 26. The phase lag, due to line and instruments, between the original emission and the arrival of the tell-tale impulse is allowed for by relative adjustment of the distributer rings 5, 26, Fig. 4 (not shown). Both impulses occur during the same revolution of the brushes, Fig. 2 (not shown). Electric synchronous movements. Before message-sending begins, synchronizing-impulses are transmitted at the rate of one per revolution of the distributers and pass at first via ring 75 of the synchronizing distributer through magnet A, which acts to advance the brushes by means of a differential gear, Fig. 4 (not shown). This action continues till synchronism is attained, and then the synchronizing- impulses pass through the middle segment 77, whereupon magnet 110 pulls up (so that message signals arriving upon ring 75 shall be cut off at 81 and prevented from interfering with synchronism) and the neon indicator lamp 112 is lighted. Thereafter if the brushes run slow or fast, synchronizing-impulses pass through segment 76 or 78, as the case may be, and through the advancing-magnet 84 or retarding-magnet 106, and meanwhile the contact 81 is kept open by a dash-pot. The receiver brush 28<1> and tell-tale transmitter brush 7<1> are on the same shaft and are in phase with one another ; but at the originating station the distributer rings of the transmitter and tell-tale receiver are adjusted to allow for phase-lag due to instruments and line. Punching cards. Instead of forming part of a type-writer keyboard, the keys 1 may operate contacts for controlling electrically actuated punches as described in Specification 238,553, [Class 31 (ii)], Figs. 5, 6, 7, (not shown). The position in which a hole is punched corresponds to the distributer segment over which the relevant impulse is sent, and tell-tale impulses are checked back to the transmitter by the act of punching at the receiver. Specification 374,511, [Group XIX], also is referred to.